It is known that a polymer having at least one reactive silicon group in its molecule has a nature that the polymer is crosslinked through formation of siloxane bonds, which follows hydrolysis reaction or the like of the reactive silicon group due to moisture or the like, even at room temperature, so as to give a rubbery cured product.
Out of such polymers having a reactive silicon group, organic polymers having a main chain skeleton made of polyoxyalkylene based polymer or polyisobutylene based polymer are disclosed in (Patent document 1), (Patent document 2) and the like, and have already been industrially produced and have widely been used for sealants, adhesives, paints and the like. Curable compositions containing a polymer having a main chain skeleton made of polysiloxane, in particular, diorganopolysiloxane have also been reported in many documents such as (Patent document 3).
Curable compositions used for sealants, adhesives, paints and the like, and rubbery cured products obtained by curing the compositions are required to have various properties such as curability, adhesiveness, and mechanical properties.
Curable compositions containing a polymer having a reactive silicon group are cured by use of a curable catalyst. Usually, an organotin catalyst having a carbon-tin bond, such as dibutyltin bis(acetylacetonate) has widely been used. In recent years, however, about organotin compounds, the toxicity thereof has been pointed out. Thus, organotin-free catalysts have been desired to be developed.
Many researches have been made on metal carboxylates, metal alkoxides, and the like as organotin-free catalysts. Among them, carboxylic acids or amine compounds are catalysts containing no metal, and are expected to give only relatively small effects onto the environment. (Patent document 4) discloses that use of a combination of a carboxylic acid with an amine gives a curable composition having a good curability. However, in curable compositions which are cured by a silanol condensation catalyst in which an amine compound and a carboxylic acid are used in combination, the resultant cured products cannot easily gain a sufficient adhesiveness. Thus, some of the compositions are unsuitable for sealants, adhesives and the like. As stated in (Patent document 4), sufficient curability is not easily obtained by use of a silanol condensation catalyst containing an amine compound alone.
In the meantime, (Patent document 5 to 11) each disclose a curable composition using BF3 or a complex thereof as a catalyst. However, even when the catalyst is used, there arises a problem that a sufficient curability cannot be obtained in the case of further using filler, or in some other case.    Patent document 1: JP-A-52-73998    Patent document 2: JP-A-63-6041    Patent document 3: JP-A-55-43119    Patent document 4: JP-A-05-117519    Patent document 5: JP-A-2005-54174    Patent document 6: JP-A-2006-52296    Patent document 7: JP-A-2006-199721    Patent document 8: JP-A-2006-199725    Patent document 9: JP-A-2006-199730    Patent document 10: JP-A-2006-199905    Patent document 11: JP-A-2006-199906